<mat-card style="margin: 60px 20px 50px 20px">
    <div class="row justify-content-center">
        <div class="col-md-8">
            <div [hidden]="!errorMessage">
                <div class="alert alert-danger">{{errorMessage}}
                </div>
            </div>
            <br>
            <div [hidden]="!error403" class="alert alert-danger">
                未登录或超时退出，请重新登录...
            </div>
        </div>
    </div>
</mat-card>
